Method and apparatus for compressing gases



Oct. 3, 1933. N. c. cHRlsTENsEN METHOD AND APPARATUS FOR COMPRESSING GASES Filed April 8, 1930 3 Sheets-Sheet l OQGG 006.00.00

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Oct. 3, 1933. N. c. cHRlsTENsEN METHOD AND A PPARATUS FOR COMPRESSING GASES 3 Sheets-Sheet 2 Filed April 8, 1930 Oct 3 1933. N. c. cHRls-VENSEN 1,929,350

METHOD AND APPARATUS FOR COMPRESSING GASES Filed April 8, 1950 A 3 Sheets-Sheet 3 f/VVE/V TOR Patented Oct. 3, 1933 NIETHOD AND APPARATUS FOR COIWPRESSING GASES Niels C. Christensen, Salt Lake City, Utah Application April 8, 1930. Serial No. 442,674

7 Claims. (Cl. 2230-83) This invention relates to methods and apparatus for compressing and expanding gases. Its primary object is to secure a substantially or approximately isothermal compression, or expansion, of the gases. It aims to bring about such substantially isothermalcompression or expansion by means of relatively simple and mechanically efcient means. I

As is Well known to mechanical engineers, the discovery of an efficient method and apparatus for securing isothermal compression of gaseous media would bring about a great improvement in many phases of mechanical engineering. For example, the cost of compressing air for various uses would be appreciably reduced as would also the cost of compressing other gases for storage or for liquefaction. Important engineering economies would also be secured in enterprises using compressed air for power purposes, in the field of mechanical refrigeration, in the compression of various gases for storage or transportation, in the liquefaction of gases for storage or transportation, and in many other allied fields. In the production of sub-atmospheric pressures for various applications of differentdegrees of vacuum, in many engineering elds, the introduction of an efcient means of producing isothermal comd pression would also result in very important economies.

Important as are the foregoing improvements which may be secured by an eicient method and apparatus for isothermal compression of gases, they appear of little importance when compared with the revolutionary improvements which may be brought about in the field of power generation from the application of heat to gaseous working media. In this eld a revolutionary improvement in the thermal eiciency of many types of heat engines may be brought about by means of an isothermal compression of the gaseous working medium. Thermal efficiencies which are truly remarkable but hitherto not realizable because of the lack of a suitable method and apparatus may be secured by the use of my invention in connection with diiferent types of internal and external combustion engines operating with various cycles upon gaseous working media.

The substantially isothermal compression obtained by my invention is secured by keeping the gas in intimate heat transfer contact with a cooling medium during the period` of compression, so that the heat of compression is carried away as rapidly as it is generated thus preventing a rise of temperature within the gas being compressed.

One essential feature of my invention by which this substantially isothermal compression is brought about consists in the use of a fluid piston operating within a closed compression chamber, which is alternately lled and emptied by the :duid piston, allowing the compression chamber to fill with the gaseous medium to be compressed as the uid leaves the chamber and thereafter compressing the gaseous medium and discharging it as the uid fills the chamber.

Another essential feature of my invention by which the substantially isothermal compression is secured consists of means, placed within the compression chamber or connected with compression chamber, of keeping the gas during compression in intimate heat transfer contact with a cooling medium.

Similar means for circulating and mixing the cooling medium is also provided so as to maintain the highest efficiency of heat transfer.

A number of different methods of applying my invention in a variety of different forms of my apparatus may be used, but the important and o essential feature of my invention which is the basis of all of these diiferent arrangements is the combination of a liquid piston with means for bringing the gases into intimate heat transfer contact with a heat transfer medium during their compression. Some of the possible methods and different forms of apparatus for carrying out my invention are shown in the accompanying drawings. From these and the descriptions of them given below it will be apparent that the essential features of my invention may be used in a large number of different ways and in a variety of different forms of apparatus. 'Ihe methods and forms of apparatus described in the following are therefore illustrative and. I do not therefore desire to'be limited specically to these except as illustrative and as interpreted and embodied in the accompanying claims.

Figures 1, 1A and 1B show vertical sections of the simplest form of my invention with a simple heat transfer arrangement enclosed by the compression cylinder consisting of suitable coils or tubes through which a suitable fluid cooling (or heating, for expansion) medium is circulated. Figures 2, 3 and 3A show vertical sections of forms of the device in which the gaseous medium being compressed (or expanded) is circulated in contact Wih the cooling or heating coils by means of a fan Within the compression chamber. Figure 4 Shows a form of the invention in whichthe gas no to be compressed is brought into contact with a spray of the cooled compression liquid by means of a circulating pump and spray. Figure 5 shows a form of the invention in which the gas to be compressed is circulated by means of a fan in contact with a spray of the compression liquid which is cooled by contact with heat transfer coils. Figures 6 and 7 show forms of the invention in which the gas to be compressed is cooled by contact with a spray of the compression liquid thrown by a floating spray cylinder, the compression liquid being cooled by the circulation of a suitable cooling fluid through the jacket around they cylinder or by circulating the compression liquid through an external heat interchanger. Figure 8 shows a cross section on line 8-8 of Figures 2, 4, and 5, showing a method of baffling to prevent surging of the compression fluid. Figure 9 shows a preferred method of arranging the compressors, or expanders, in pairs with suitable connecting pipes and control valve.

The various methods of maintaining the intimate heat transfer contact of the gaseous medium during compression with a suitable cooling medium so as to secure substantially or approximately isothermal compression and of compressing and discharging the gaseous medium during this intimate heat transfer contact are important and essential features of my invention illustrated in the drawings and described in the following brief description.' These same methods are also applicable with the invention for substantially or approximately isothermal expansion of the gaseous working medium. As previously noted, this substantially or approximately isothermal compression or expansion is obtained by the combination of a fluid piston operating in a cylinder containing suitable means bringing the gases being compressed or expanded into intimate heat interchange contact with a suitable heat transfer medium. The compression (or expansion) and the expulsion of the gaseous medium from the compression cylinder containing these means of heat transfer from (or to) the gaseous medium, is secured largely by means of the liquid piston which is an important feature of the invention.

The simplest form of my invention is illustrated in Figures 1, 1A and 1B. It consists of a compression chamber or cylinder 1) (of any desired or suitable form but preferably cylindrical), a suitable liquid (L) which forms the fluid piston within the compression chamber or cylinder (1), a pump (2) for forcing the liquid (L) into the compression chamber (1) cooling coils or radiator pipes (3) within the cylinder exposing a relatively very large heat transfer surface to the gaseous medium and the compression liquid (L), a gas inlet pipe (4) and valve (5) for supplying the gas to be compressed to the cylinder (1), a compressed gas outlet pipe (6) and outlet valve (7) for discharging the compressed gas, a countercurrent heat interchanger (8) for cooling the heat interchange fluid passed through the cooling coils (3) together with a suitable inlet pipe (9) and a suitable outlet pipe (10) and a pump or fan (31) for circulating the cooling fluid through the cooling coils or radiator (3). Figures 1, 1A and 1B show different forms of cooling tubes. The device is preferably arranged in pairs as shown in Figure 9, the pump (2) alternately supplying and withdrawing the compression liquid (L) to and from'the cylinders (l) through the valve (11) and liquid inflow pipes 12) and outflow pipes (13). The control valve (11) consists of a stationary part (14) having five ports, two

inlet ports (15A and 15B) and two outlet ports (16A and: 16B), a pump port (19), and a rotating part (20) with three connected radiating passages (21) so arranged that they connect in one v fixed position with the pump port (19) and an inlet port (15B) and outlet port (16A) and in the other xed position with pump port (19) and the inlet port (15A) and the outlet port (16B). This valve (11) is so arranged that when in one position it allows the compression fluid to be withdrawn from one of the pair of compression cylinders and to be pumped into the other compression cylinder, and when the fluid piston has filled the latter cylinder, the valve is automatically shifted so that the compression fluid (L) is withdrawn from the latter and pumped into the former. This automatic operation of the valve may be secured by means of floats within the cylinders (l) arranged to close and open an electromagnetic circuit operatng the devices for shifting the valve (1l) at the required points in the cycle of operation. Such control system may be of .either the electro-magnetic type or the combination electro-magnetic-compressed air type and requires no detailed description as such sys- 10() tems are well known and in common use.

The operation of the invention is briefly as follows: As the compression liquid (L) is withdrawn from the compression cylinder (1) the valve (preferably a check valve) (5) opens allowing the 105 gas to be compressed to enter through the inlet pipe (4) and ll the cylinder (1) After the filling of the cylinder (1) with the gas to be compressed, the pump (2) (of any desired type, either piston or centrifugal, but preferably of the piston type to secure highest efficiency), pumps the liquid (L) into cylinder 1) and as the liquid piston lls the cylinder the gas is compressed and finally discharged through the outlet valve (7) and compressed gas outlet pipe (6).` Dur- 115 ing this compression the cooling fluid (air or water or other cooling fluid) is circulated by the pump (31) through the cooling coils or radiator (3) enclosed by the cylinder (1) in heat transfer contact with the gas being compressed by the liquid piston, cooling the compressing gas by absorbing the heat of compression and preventing any large rise in temperature, i.e., securing an approximately or substantially isothermal compression. The coils or radiator (3) should expose the maximum possible amount of heat transfer surface to the gas being compressed inV this form of apparatus in order to secure efficient heat transfer since there is relatively little circulation of the gas in contact with the cooling surfaces except that secured by convection. The nearness of the approximation to isothermal compression will therefore depend upon the amount of heat transfer surface exposed and the a temperature of the cooling fluid in the cooling coils. `By keeping the temperature of the cooling fluid in these coils (3) considerably below the temperature at which it is desired to compress and discharge the gas, a substantially isothermal Y compression may be secured. It is also apparent thatit would also be possible by the use of very low 'temperatures in the cooling coils (3) to compress the gases with vdecreasing temperature during the compression.

It will be noted that the complete compression portion of the cycle is made up of a number of short compression periods corresponding with the outlet stroke of the pump (2) with intermediate periods of rest during the intake stroke of the150 pump (2) The complete compression may therefore be compared to a large series of multiple compressions with intermediate cooling, for if the cooling during each small compression period is not complete it is continued during the intermediate periods of rest.

As noted above the device is preferably operated in pairs as shown diagrammatically in Figure 9 so as to allow continuous operation of the pump (2) and so as to avoid loss of power due to pumping the compression liquid to a higher elevation which would occur if the compression liquid was not returned through the pump (2) after the compression and during the gas. filling portion of the cycle. With the device operated in pairsgthe pump withdraws the compression liquid (L) from one cylinder (1) allowing this cylinder to ll with the gas to be compressed and at the same time pumps the compression liquid (L) into the other cylinder (1) compressing and discharging the compressed gas, the control valve (11) being automatically shifted at the end of each cycle so that the operation is reversed in each compression cylinder. The manner in which this is accomplished by means of the valve (1l) is shown in Figure 9. During compression in the cylinder A, and gas filling in the cylinder B, the valve (11) is in the position shown so that the compression liquid L from B is withdrawn through the pipe (13), check valve (17B), port (15B) and port (19) to the pump (2) and forced by the pump through the ports 19) and (16A) and check valve 18A and pipe 12 into the cylinder A. When the compression and discharge is completed in cylinder A, the rotating part (20) of the valve is automatically shifted so that the passages (21) allow the ilow of compression liquid (L) from the cylinder A through the pipe (13) check valve (17A) port 15A and port (19) to the pump (2) and from the pump (2) through the ports (19) and (16B) and check valve (18B) and pipe (12) to the cylinder (B). The shifting of the valve (11) is arranged to take place during an intake stroke of the pump so as to avoid damage to the pump.

If desired, the flow of cooling 'uid through the radiator or cooling coils or tubes (3) may also be arranged so that the circulation occurs only duringljcompression by means of an automatic two way valve (22) arranged in the pipes (9) as shown in Figure 9 and shifted at the same'time as the valve (11) If free air or water is used for cooling and is not re-circulated, the counter-current cooler (8) may be dispensed with but the shifting valve (22) may still be used so as to eliminate circulation of the cooling iiuid in the coils (3) during intake of gas to be compressed.

I t will be obvious that-if the invention is to be used for isothermal expansion, the compressing operation described in the foregoing will merely be reversed, sufficient compressed gas to fill the cylinder (1) when expanded being admitted through a suitable automatic inlet valve in the inlet pipe (4) which may be regulated and controlled by a oat and automatic control system in the same manner as valve (11), and the expanded gas being released through a similar automatically controlled valve in the outlet pipe (6) the pump (2) in this case acting as a power generator instead of supplying power, and the coils (3) supplying heat to the expanding gas instead of abstracting heat from the compressing gas. As previously mentioned, the main value of the invention is for compression rather than for expansion and the main emphasis in the depression is obtained by a combination of a cirj;

scription and drawings is therefore upon the use of the invention as a compressor.

To increase the rate of heat transfer from the gas during compression and thus increase the capacity of the device and at the same time secure approximately or substantially isothermal compression, the gas under compression may be rapidly circulated in contact with the cooling pipes or radiator (3) within the compression chamber (1) by means of a fan (24) as shown in Figures 2, 3 and 3A. In this form of the device the cooling coils or radiator (3) may be distributed through the chamber (l) as shown in Figures 3 and 3A or may be concentrated mainly in the discharge space above the compression space as shown in Figure 2. In both of these forms of the invention, the gas during compression is rapidly circulated in contact with the cooling coils or pipes (3) by means of the circulating fan (24). Except for the addition of the circulating fan (24) and rearrangement of the cooling coils or pipes (3) this form of the invention is similar to that of Figure 1, and should preferably be operated in pairs as shown in Figure 9 with the compression pump (2) and valve (l1) 100 arranged as previously described. The operation of the forms of the device shown in Figures 2 and 3 is similar to that of the form shown in Figure 1 except that during compression the fan (24) is in motion but as the compression fluid 105 rises to discharge the compressed gas the fan is automatically stopped by breakingthe electric circuit bymeans of a suitable float within the chamber (1) (or by any other suitable method) so that while-the liquid (L) covers the fan (24)y 1l.' in discharging the compressed gas the fan is stationary. The fan (24) is preferably not started again until compression begins again, though it may be started if desired during intake of the gas after the liquid (L) has fallen below the level 115 of the fan during the intake portion of the cycle.

Figure 4 shows a form of the device in which the gas during compression is cooled by contact with a spray of the compression liquid (L). In this form the compression liquid (L) is circulated 120 through the spray nozzles or coil (25) near the top of the compression chamber by means of the circulating pump (26)v and circulating pipe (27).

In this circulation the liquid (L) passes through the counter-current heat interchanger or cooler 125 (8) and the heat of compression absorbed during the spraying operation within the cylinder is withdrawn by heat interchange contact with a suitable cooling medium such as air or water. If desired, cooling coils may be used within the 330 compression cylinder in conjunction with the spray 26). This form of the device is also preferably operated in pairs with the pump (2) and valve (11) arranged as in Figure 9 and operated as previously described. In this case the circulating pump (26) should preferably be arranged to supply the spray for both of the pair of' cylinders (l) by means of an automatic valve in the circulating pipe (27) arranged to allow circulation of the fluid (L) to the sprays alternately to each of the pair of compression cylinders during the compression part of the cycle in each.

Figure 5 shows an arrangement of the invention in which the cooling of the gas during comculating fan (24) and rotor spray (28) and cooling coils (3) arranged in the upper or discharge portion of the compression chamber or cylinder (1). In this form of the invention the cooling coilsl (3) are grouped in the path of the spray 15G thrown by the rotating cylinder (28) and the fan (24) circulates the gas being compressed through the spray of liquid (L) being thrown by the cylinder (28). Beneath the cylinder (28) is a basin (29) arranged to fill the compression liquid (L) as the liquid (L) rises at the end of compression part of the cycle and lls the upper part of the cylinder (l) during the expulsion of the compressed gas. As the liquid (L) falls during the intake of gas, the basin (29) retains some of the liquid (L). The rotor spray dips slightly into this liquid in the basin (29) and when rapidly rotated throws a spray ofthe liquid onto the cooling pipes (3), the sprayed liquid constantly returning to the basin (29) down the walls of the chamber (1)1 above the basin which latter ex- -tends between the walls of the chamber (1) at right angles to the section shown in the drawings. The baffles or eliminators (30) prevent the carrying away of any spray from the basin (29) by the gas circulated by the fan (24). tion of this form of the device will be apparent from the foregoing. During the compression of the gas in the cylinder (1) by the liquid piston (L) forced into the cylinder (1) by the pump (2) the gas under compression is passed through the spray thrown by the rotating cylinder (28) and gives up its heat to the sprayed liquid which in turn transfers this heat to the cooling fluid (air, water or other medium) circulated through the coils (3) By this means a very efcient cooling is secured which prevents heating of the gas during compression. If the cooling fluid circulated through the coils (3) is kept at a low enough temperature, the compression may be substantially isothermal, or the gas may even be cooled during compression if the circulating fluid is kept at sufciently low temperature. After compression of the gas to the desired pressure the power operating the fan (24) and spray rotor (28) is automatically cut off and they remain stationary while the liquid piston (L) rises and submerges them anddischarges the compressed gas through the outlet valve ('7) and outlet pipe (6). The cooling fluid (air, water or other medium) circulated through the coils (3) may be circulated through the counter current heat interchanger (8) or if free air or water is used, which is not cooled and reused, the cooler or heat interchanger (8) may be dispensed with.

The form of the invention shown in Fig. 5 is also preferably used in pairs as shown in Fig. 9, with the valve (11) arranged so that the pump (2) supplies the compression liquid (L) to each of the pair of compression cylinders (1) and also with the valve (22) in the cooling circuit arranged so that the flow of cooling medium is supplied alternately to each cylinder during the compression cycle.

It will be noted that in the forms of the invention shown in Figs. 2, 3 and 5 the portion of the compression chamber or cylinder (l) above the base of the cooling devices (coils, fan, spray rotor, etc.) is the discharge space and below this level is the compression space within the cylinder (1). With the forms shown in Figs. 1 and 4 there is no fixed level between the compression and discharge space.

Figs. 6 and '7 show two forms of the invention in which the gas is cooled during compression by a spray of the compression liquid (L) thrown by a revolving spray cylinder (28) carried by a float (32) within the compression chamber (1) which supports the cylinder (28) at such a level that it dips slightly into the surface of the liquid The opera- (L) and as it revolves throws a spray of this liquid filling the cylinder (l) above the level of the surface of the liquid piston. During compression the heat in the gas is transferred to the sprayed liquid which is cooled by circulation of a cooling fluid (air, water, etc.) through the jacket (33) surrounding the cylinder (1), as shown in Figs. 6 and '7, or by circulation of the liquid (L) in closed circuit through an external jacket or heat interchanger, by the circulating pump (31) In the arrangement shown in Fig. 6, the rotor cylinder (28) must be driven by a motor within the compression chamber (l) This may be done by making the cylindrical shell (28) part of the external rotor (34) of the motor and fastening the central stator (35) to the float as shown in Fig. 6, the rotor (34) being carried on the shaft (36) which supports the stator by means of the revolving hollow cylindrical bearings (37). In this case a compressi-on liquid (L) which will not affect the motor windings must be used and the electric power must be carried to the motor by a flexible cable. The arrangement of Figure 7 differs from that of Fig. 6 only in that in thel latter, the float (32) which supports the rotor spray is held in a fixed path during its ascent and descent with the rise and fall of the liquid piston (L) by a pair of arms (38) instead of the vertical shaft (39) and guide (40) as used in the arrangement of Fig. 6. In both arrangements of Figs. 1. and 6 the rotor (34) is arranged to revolvev during compression and the power is cut off during discharge of the compressed gas so that rotor 34) is stationary during the period of discharge, while it is partially or fully submerged in the liquid (L), and also preferably during the intake part of the cycle, while the' liquid piston (L) is descending. The forms of the invention shown in Figures 6 and '7 are also preferably operated ini pairs as previously described and as diagrammatically shown in Fig. 9.

` Figure 9 is a diagrammatic drawing showing the preferred arrangement of all forms ofthe apparatus in pairs. Though the means of cooling the gas during compression is that of Figure 2 any of the different forms of cooling arrangement may be used.

As previously noted in connection with the description of the form of the invention shown in Fig. 1, any of these forms of the invention -may be used to secure approximately or substantially isothermal expansion of gases by making the changes suggested in the description of Fig. 1. This will be apparent without further extended discussion.

Any -suitable liquid may be used as the compression fluid or liquid piston (L) accordingto the purpose for which the invention is used. In most cases water or oil will be used, but otherA liquids or solutions ofvvarious kinds may be used.

It must be understood that the cooling (or heating) of the gaseous medium in the compres-A sion chamber may be controlled by the rate of circulation and temperature of the cooling medium in cooling coils (3) (or the circulation and temperature of the compression liquid L when this is used as the cooling medium) and that the use of the invention is not confined to compression (or expansion) at any definite temperature or to substantially or approximately isothermal compression (or expansion) but may be used for any controlled cooling (or heating) of the gaseous working medium used in the operation of the invention. Its greatest usefulness is Uli however for approximately isothermal compression.

For high compression it will be advantageous to connect a number of the cylinders (1), preferably in pairs as described, in a series using a number of cylinders (or pairs of cylinders) for the low pressures and decreasing the number of cylinders in each step of the series in proportion to the increase in pressure. All the pumps for such a series should be driven from a common shaft and'so arranged, as to phase, as to equalize the power required.

From the foregoing it will be apparent that my invention may be carried out in a variety of forms and arrangements of the essential parts of the apparatus and that various combinations of the methods of cooling the gas during compression (or heating the gas during expansion) may be used without departing from the main features and spirit of the invention. For these reasons I do not desire to be limited entirely by the designs or arrangements shown and described except as these are illustrative and as they are interpreted in the claims.

Having described my invention and shown some of its practical applications what I claim and desire to patent is:

1. The method of compressing and cooling gases which consists in pumping a liquid into a closed compression chamber containing said gas, circulating said gas in contact with cooling tubes enclosed by -said chamber, circulating a iluid cooling medium through said tubes, thereby absorbing and withdrawing heat from said gas in said chamber. l

2. The method of securing approximately isothermal compression ofgases which consists in pumping a liquid medium into a closed compression chamber containing said gas, circulating said gas in contact with cooling tubes enclosed by said chamber, circulating a fluid cooling medium through said tubes during said period of compression, thereby absorbing and withdrawing heat from said gas in said chamber.

3. The method of compressing and cooling gases and thereafter discharging the compressed gases which consists in pumping a liquid medium into a closed compression chamber containing said gas, circulating said gas in contact with cooling tubes enclosed by said chamber, circulating a fluid cooling medium through said tubes, thereby absorbing and withdrawing heat from said gas in said chamber, and, after compressing said gas by partially lling said chamber with said liquid medium, discharging said gas from said chamber by llng said chamber with said liquid medium by continuing said pumping operation.

4. The method of compressing and cooling gases which consists in pumping a liquid medium into a closed compression chamber containing said gas, spraying said liquid medium into contact with said gas, and into contact with cooling tubes enclosed by said chamber, circulating said gas in contact with said sprayed liquid, and passing a cooling fluid through said cooling tubes, thereby absorbing and withdrawing heat from said gas in said chamber by said cooling uid.

5. The method of securing approximately isothermal compression of gases which consists in pumping a liquid medium into a closed compression Achamber containing said gas, spraying said liquid into contact withsaid gas and into contact with cooling tubes enclosed by said chamber, circulating said gas in contact with said sprayed liquid and passing a cooling fluid through said tubes during said period of compression, thereby absorbing and withdrawing heat from said gas in said chamber by said cooling fluid.

6. The apparatus for compressing and cooling gases which consists of the combination of a closed compression chamber, a liquid compression medium, a pump for pumping said liquid medium into said compression chamber, cooling tubes enclosed by said compression chamber, means for circulating gas Within said compression chamber in contact with said cooling tubes, and means for circulating a cooling fluid'through said cooling tubes.

7. The apparatus for compressingI and cooling gases which consists of the combination of "a closed compression chamber, a liquid compression medium, a pump for pumping said liquidinto said compression chamber, means for spraying said liquid into :contact with said gas in said chamber, means for circulating said gas in said chamber in contact with said sprayed liquid, cooling coils enclosed by said chamber, and in con-' tact with said sprayed liquid, and means for passing a uid cooling medium through said cooling coils.

NrELs C. crmIsTENsEN. 

